Method and apparatus for locomotive fuel tank repair

Information

  • Patent Grant
  • 6378188
  • Patent Number
    6,378,188
  • Date Filed
    Friday, August 18, 2000
    24 years ago
  • Date Issued
    Tuesday, April 30, 2002
    22 years ago
Abstract
A method for preparing a fuel tank for repairs and verifying the repair work using an apparatus is presented. The apparatus is connected to the fuel tank. The fuel tank is purged of oxygen to a certain level using a gas provided by the apparatus until a level of the oxygen in the fuel tank reaches that level. Openings on the fuel tank are closed to the environment. The fuel tank is repaired while the level of oxygen is maintained in the fuel tank. The gas provided by the apparatus pressurizes the fuel tank to a certain pressure level. The pressure level is maintained for a specified period of time. An inspection of the repaired area of the fuel tank is then performed.
Description




BACKGROUND OF THE INVENTION




1. Field of Invention




Aspects of the present invention generally relate to a method and apparatus for facilitating the repair of a fuel tank and testing of repair work. More specifically, aspects of the invention relate to a system and related method for preparing a fuel tank for repair by hotwork by rendering the tank non-reactive and testing the repair work upon completion by pressurizing the tank.




2. Description of Background Information




On occasion, fuel tanks acquire tears, cracks, and holes that require repair. Some repairs require the use of so-called hotwork, i.e., welding. However, when such repair work is to be completed on a fuel tank, there is always concern for the potential of a fire or explosion.




In order for a fire or an explosion to occur, three elements are required—an ignition source, fuel, and oxygen. Since welding is necessary to repair the tank, in order to avoid a fire or an explosion, elimination of either an oxygen source or a fuel source during such repair is necessary.




In the marine and petroleum industries, welding on tanks containing combustible or flammable substances is sometimes achieved by inerting the tank's atmosphere. Inertion of a tank involves blowing gas, such as carbon dioxide or nitrogen, into the tank, rendering the tank environment inactive by reducing the oxygen content by replacing it with an inert gas. To verify the repair work, the tank is ventilated and a localized air or fire hose test is performed on the repaired area. In this industry, these methods of testing repair work involve placing a human inside the tank to look for air or water leaking into the tank during such air or fire hose tests. Due to the size of these fuel tanks, it is not practical to test the entire tank.




Unlike the marine industry, the common method of repairing a fuel tank using hotwork involves draining the fuel from the tank and steaming the inside of the fuel tank, reducing the fuel hydrocarbon levels to below a lower explosive limit. This renders the tank safe for repair by hotwork.




Verifying tank repairs in the locomotive industry also differs from the marine industry. Locomotive fuel tanks are not large enough to place a human within to test repair work. One common method to verify repair work in the industry is to use a standing water test, where the repaired tank is filled with water above the repaired area and the repaired area is inspected externally for any leaking water.




In the locomotive industry, as with any industry, there is always an ongoing need to develop new methods and techniques for procedures. Thus, there remains a need in the locomotive industry to develop a method for preparing a tank for hotwork repair and testing the repair work.




In addition, each of these processes—preparing a fuel tank for repair by welding and testing the repair work—requires the use of different equipment. Currently, there is no comprehensive equipment capable of performing both of these processes to repair work. Thus, there remains a need for such equipment in the locomotive industry, as well as in other industries.




U.S. Pat. No. 3,590,559 (Bragg et al), herein incorporated by reference in its entirety, discloses an inerting system to prevent fires and explosions in fuel tanks by removing dissolved oxygen in the fuel when pressure changes within the fuel tank.




U.S. Pat. No. 5,668,308 (Denby), herein incorporated by reference in its entirety, describes a method of detecting leaks in storage tanks by pressurizing the tank and measuring the drop in pressure over a specified time period. Similar U.S. patents exist for testing motor vehicle's evaporative fuel systems by pressuring the tank and measuring the change in pressure over time.




Currently, there remains a need for improved effective methods to prepare a locomotive fuel tank for hotwork repairs and to test the repair work. Also, there is a need for comprehensive equipment that performs both of these functions. In addition, there remains a need for an apparatus and method that allow repairs to be performed and verified back-to-back until the repair is, in fact, complete.




SUMMARY OF THE INVENTION




An embodiment of the present invention includes an apparatus for preparing a fuel tank for repairs and verifying repair work upon completion. The apparatus includes a supply system constructed and arranged to be coupled to the fuel tank for providing a supply of inert gas into the fuel tank, for purging the fuel tank of oxygen to a certain level and for making inert the fuel tank with the gas. The supply system includes a gas release system constructed and arranged to provide the supply of inert gas. The supply system further includes an arrangement for connecting and facilitating transport of the inert gas. A supply mechanism is configured and positioned to facilitate and regulate a transfer of gas from the gas release system to the fuel tank. A connector mechanism is for coupling the supply mechanism to the gas release system. A relief system is constructed and arranged to be coupled to the fuel tank to regulate and relieve pressure in the fuel tank. A plurality of connectors is for connecting the apparatus system to the fuel tank. The plurality of connectors include a first of the plurality of connectors constructed and arranged to couple the supply system to the fuel tank, and a second of the plurality of connectors constructed and arranged to couple the relief system to the fuel tank.











BRIEF DESCRIPTION OF THE DRAWINGS




The above and other objects, features, and advantages of the present invention are further described in the detailed description that follows, with reference to the following drawings wherein:





FIG. 1

is a system diagram of one embodiment of the fuel tank repair apparatus;





FIG. 2

is an operational flow diagram corresponding to the method implementing the fuel tank repair apparatus during both repair and testing of the repair work; and





FIG. 3

is an operational flow diagram corresponding to the method implementing the fuel tank repair apparatus during the testing of the repair work.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT





FIG. 1

illustrates an embodiment of an apparatus for locomotive tank repair preparation and testing in accordance with the present invention, designated generally by the reference character


10


. As shown, apparatus


10


comprises a supply system, generally indicated at


30


, a relief system, generally indicated at


70


, and a plurality of connectors.




In this embodiment, the plurality of connectors comprises two connectors, supply side connector


12


and relief side connector


14


. Supply side connector


12


and relief side connector


14


couple a fuel tank


20


to supply system


30


and relief system


70


, respectively. In the illustrated embodiment, each of supply side connector


12


and relief side connector


14


, is a four-foot length of hose, although other lengths can be used. One end of each hose thereof is connected to a respective fuel filler tank adapter (not shown). The fuel filler tank adapters attached to one end of each of supply side connector


12


and relief side connector


14


connect to fuel fixtures on fuel tank


20


. The other end of each of supply side connector


12


and relief side connector


14


are coupled to passages on the supply system


30


and the relief system


70


, respectively.




Supply system


30


comprises a connecting mechanism


36


, a gas release system


40


, and a supply mechanism


50


. Connecting mechanism


36


in the form of a hose couples gas release system


40


to supply mechanism


50


. In the illustrated embodiment, gas release system


40


comprises a gas supply


42


and a gas supply arrangement


44


. To render the fuel tank's


20


environment safe for repair by hotwork, gas supply


42


is a supply of gas capable of rendering the environment of fuel tank


20


non-reactive. Gas supply


42


in this embodiment includes four full 50-lb. cylinders of nitrogen gas, but may include additional or fewer cylinders of different sizes. While nitrogen gas is used in this embodiment, other gases capable of inerting fuel tank's


20


environment are also appropriate.




Gas supply arrangement


44


includes an arrangement of valves and passages for transporting gas from gas supply


42


to fuel tank


20


. Gas supply arrangement


44


, in the illustrated embodiment, is a four cylinder manifold stand system for attaching four cylinders


42


of nitrogen gas to its four outlets, each cylinder and outlet having its own valve


41


, with a master valve


46


.




High pressure regulating mechanism


32


is coupled to gas supply arrangement


44


and high pressure relief mechanism


34


. High pressure regulating mechanism


32


regulates the flow of gas passing from gas supply arrangement


44


to supply mechanism


50


. High pressure relief mechanism


34


relieves pressure in supply system


30


if the pressure exceeds a particular level. In the illustrated embodiment, high pressure regulating mechanism


32


and high pressure relief mechanism


34


are a high pressure regulator and a high pressure relief valve set for 200 psi, respectively.




Supply mechanism


50


is coupled to high pressure regulating mechanism


32


with high pressure relief mechanism


34


. In the illustrated embodiment, the coupling of these elements is achieved using a length of hose, such as a 15-foot long air duct hose.




In the illustrated embodiment, supply mechanism


50


comprises an arrangement of a plurality of flow control mechanisms, a plurality of passages, a supply side pressure regulating mechanism


52


, a supply side pressure measuring mechanism


54


, and a flow meter valve


56


, as shown in FIG.


1


. In the illustrated embodiment, the plurality of flow control mechanisms comprises nine valves


21


,


22


,


23


,


24


,


25


,


26


,


27


,


28


, and


29


. Supply side pressure regulating mechanism


52


is a low pressure regulator. Supply side pressure measuring mechanism


54


measures the gas pressure entering fuel tank


20


. In this embodiment, supply side measuring mechanism


54


is a pressure gauge and is considered the primary gauge.




In the illustrated embodiment, the plurality of passages comprises three passages


61


,


62


, and


63


. The plurality of passages may include an arrangement of pipes, hoses, and structures that facilitate the transfer of gas to fuel tank


20


. Passage


61


is coupled to high pressure relief mechanism


34


, and to supply side connector


12


. Passage


62


is coupled to passage


61


such that gas may flow between passage


61


and passage


62


. In a similar manner, ends of passage


63


are coupled to passage


61


.




As shown in

FIG. 1

, valves


22


,


23


,


24


,


25


, and


27


are connected in a serial configuration along passage


61


. Pressure regulating mechanism


52


is also coupled to passage


61


, interposed between valves


62


and


63


. In this embodiment, a first end of passage


62


is connected to passage


61


between valve


22


and the end of passage


61


coupled to connecting mechanism


36


. A second end of passage


62


is connected to passage


61


, interposed between valves


23


and


24


. Pressure measuring mechanism


54


is also coupled to passage


61


between valves


25


and


27


, wherein valve


26


is coupled to pressure measuring mechanism


54


in such a way that valve


26


can regulate a flow of gas to pressure measuring mechanism


54


. Passage


63


is coupled to passage


61


, wherein a first end is interposed between pressure measuring mechanism


54


and valve


27


and a second end is interposed between valve


27


and an end of passage


61


attached to connector


12


.




Valve


21


is coupled to passage


62


. Flow meter valve


56


is coupled to passage


63


. On each side of flow meter valve


56


, valves


28


and


29


are coupled to passage


63


.




Valves


21


along with passage


62


can prevent the movement of gas through passage


61


by being used as a bypass line around pressure regulating mechanism


52


in the illustrated embodiment. The use of this bypass feature is required during the purging process to permit flow meter valve


56


to operate at its design supply pressure. Valves


22


and


23


may be operated to isolate pressure regulating mechanism


52


from the flow of gas. Valve


26


can isolate pressure measuring mechanism


54


. Valve


27


may be operated to ensure that the flow of gas travels through passage


63


and past flow meter valve


56


. Meanwhile, valves


28


and


29


may be operated to isolate flow meter valve


56


.




Relief system


70


comprises a pressure measuring mechanism


72


, a plurality of pressure relief mechanisms


74


, a flow control mechanism


76


, and passage


64


. Pressure measuring mechanism


72


measures the gas pressure leaving fuel tank


20


. In the illustrated embodiment, pressure measuring mechanism


72


is a pressure gauge. In the illustrated embodiment, pressure measuring mechanism


72


is a secondary pressure measuring device. Pressure relief mechanism


74


comprises two low pressure relief valve in this embodiment, although more or less than two low pressure relief valves may be used. Pressure relief mechanism


74


relieves pressure in relief system


70


from fuel tank


20


. It is recommended that each of pressure relief mechanism


74


be capable of relieving the full capacity of apparatus


10


. Flow control mechanism


76


is a single valve


80


in this embodiment. Flow control mechanism


76


may comprise other valve or flow control configurations appropriate for controlling the pressure in fuel tank


20


. Valve


80


can be operated to prevent the release of gas through passage


64


and assist apparatus


10


with pressurizing fuel tank


20


.




Passage


64


, in this embodiment, may include an arrangement of pipes, hoses and structures that facilitate the movement of gas from fuel tank


20


. In the illustrated embodiment, one end of passage


64


is coupled to a hose end of connector


14


. In this embodiment, pressure measuring mechanism


72


, pressure relief means


74


, and flow control mechanism


76


are coupled to passage


64


in a serial configuration wherein pressure measuring mechanism


72


is closest to the end of passage


64


connected to connector


14


.





FIG. 2

generally depicts one embodiment of the method that prepares a tank for repair by hotwork and tests the repair work upon completion. This method is particularly applicable to fuel tank repair work involving small holes and cracks. However, this method can repair long tears and splits. When using this method, the remaining fuel in fuel tank


20


need not be drained prior to repair by hotwork.




In a first act A


1


, apparatus


10


is connected, via connectors


12


and


14


, to fuel tank


20


, which requires hotwork repair. In a second act A


2


, apparatus


10


purges the oxygen and inerts the environment of fuel tank


20


, rendering the environment non-reactive by entering nitrogen gas into fuel tank


20


. The fuel tank vents and/or fuel return lines must be blocked by appropriate means before inerting the environment of fuel tank


20


. In the illustrated embodiment, pipe plugs, cover plates, or a combination thereof, are used to close off the fuel tank vents and return lines on fuel tank


20


. Other appropriate materials for closing off the vents and fuel return lines to fuel tank


20


include a blanking plate and duct tape. Valve


80


is in an open position to allow the flow of gas to pass through supply system


30


and fuel tank


20


and out passage


64


.




To complete act A


2


, the valve to one bottle of gas supply


42


attached to gas release system


40


and the corresponding valve on gas release system


40


are opened. Master valve


46


is then opened. The valve to high pressure regulating mechanism


32


is adjusted until the outlet pressure reads between 50-80 psig. Valves


22


,


24


,


25


and


27


are opened along passage


61


. Valve


23


is then slowly opened. Valve


26


is opened to measure the flow of gas to fuel tank


20


. This process inerts the environment of fuel tank


20


with inert gas supply


42


and purges oxygen from the same.




Once the oxygen content in the gas escaping from valve


80


measures less than six percent, valve


80


is closed during the remainder of the inertion and purging process. Oxygen content levels are measured using oxygen detecting devices; such as a cannonball gas detector. Oxygen levels within fuel tank


20


are also measured at the drain holes. The drain holes are closed after the oxygen content of the escaping gas is below six percent.




In some instances, a hole is drilled into fuel tank


20


above the remaining fuel line to assist with monitoring of oxygen levels. In the illustrated embodiment, a cannonball probe is fed through the drilled hole to measure the oxygen content of the environment of fuel tank


20


. In these instances, the oxygen content measured at this hole must also register below six percent before hotwork repair may begin.




Once the oxygen levels at all gas escape points measure below six percent, valves


24


,


26


, and


27


are closed. Meanwhile, valves


21


,


28


, and


29


are opened. Valve


24


is then opened allowing inert gas to pass through passage


61


and past flow meter valve


56


. In the illustrated embodiment, flow meter valve


56


is set to 80 Standard Cubic Feet/hour (SCFH). The flow of gas from inert gas supply


42


should be reduced to between 80 and 40 SCFH on flow meter valve


56


. This completes act A


2


.




Purged of most oxygen and inerted by gas supply


42


, fuel tank


20


is ready for repair work by hotwork. Such repair work is conducted by conventional methods in a next act A


3


. It is recommended that gas flow from gas supply


42


should be kept at a minimum, but at a level sufficient to maintain the inert and purged environment of fuel tank


20


. In the illustrated embodiment, tank pressure in fuel tank


20


is maintained at 0.0 to 0.4 psig using flow meter valve


56


. For purposes of safety, it is also recommended that the oxygen content nearest the repair site be tested periodically during the repair to ensure the oxygen level remains below six percent.




Upon completion of the repair work in act A


3


, fuel tank


20


is pressurized to test the repair work in a next act A


4


. Act A


4


also involves preparing to pressurize fuel tank


20


by adjusting the appropriate flow control mechanisms. In the illustrated embodiment, valves


21


and


25


are closed. If a hole was drilled in fuel tank


20


above the fuel line during act A


2


, this hole is also closed. In the illustrated embodiment, the drilled hole is closed using a threaded plug inserted into a spud fitting welded to the top of fuel tank


20


. Valves


23


,


28


, and


29


are also closed. Valves


24


,


25


, and


27


are then opened. Next, valves


23


and


26


are slowly opened. To complete the preparation for pressurizing fuel tank


20


, valve


80


is closed.




Upon closing valve


80


, fuel tank


20


is being pressurized. In the illustrated embodiment, fuel tank


20


is pressurized to between 1.8 and 2.0 psig and held at this pressure for at least ten minutes before testing the repair work. To assist in regulating the pressure in fuel tank


20


, valve


24


is adjusted appropriately.




Once fuel tank


20


reaches and maintains the appropriate pressure level, personnel can verify the tank repairs by testing the repair work in a next act A


5


. In the illustrated embodiment, the inspector of the repair work conducts a visual and audible inspection. The visual inspection involves the use of a “snoop” or equivalent soap bubble solution to wet the repaired area, wherein the inspector would look for bubbles that indicate a leak in the repaired area. During an audible inspection, the inspector checks for leaking gas using the back of his or her hand. Other appropriate conventional inspection methods may be used to verify the repair work.




If a leak is found during act A


5


, corrective repair work can immediately follow in a further act A


5




a


upon closing valves


25


and


26


and opening valve


80


. When the corrective repair work is complete, valves


25


and


26


are reopened and valve


80


is closed to repressurize fuel tank


20


, as described in act A


4


. The corrective repair work can be tested in an appropriate manner, such as those methods suggested in act A


5


. This corrective repair process can be repeated iteratively until the repair work is complete. An advantage to this method is the repeated ability to verify repair work and immediately take corrective action, if necessary, until the repair is complete.




In a next act A


6


, repaired fuel tank


20


is vented, allowing the gas to escape from fuel tank


20


. In the illustrated embodiment, valve


24


is slowly closed and valve


80


is opened. Valves to the bottles of gas supply


42


are then closed; valves


21


,


22


,


23


,


24


,


25


,


27


, and


80


are open; valves


26


,


28


, and


29


are closed; high pressure regulating mechanism


32


is set for 50 psig; and pressure regulating mechanism


52


is set to 2-3 psig. After apparatus


10


is appropriately adjusted, the fuel tank plugs and tank vent cover are removed. Then, apparatus


10


may be disconnected from fuel tank


20


, and fuel tank


20


is assembled appropriately for normal use.




A user of the above described method may also opt to implement only one aspect of the invention, namely the preparation of fuel tank


20


for repair by hotwork or testing of repair work.

FIG. 3

generally depicts one embodiment of a user employing apparatus


80


and the method for testing repair work. In a first act B


1


, fuel tank


20


is repaired by conventional methods, such as draining the remaining fuel and steaming fuel tank


20


to reduce hydrocarbon levels in fuel tank


20


to less than the lower explosive limit. In a second act B


2


, apparatus


10


is attached to repaired fuel tank


20


as in act A


1


in FIG.


2


. With apparatus


10


connected to repaired fuel tank


20


, repaired fuel tank


20


is pressurized in a next act B


3


, in a manner in accordance with act A


4


. In a next act B


3


, the repair work on fuel tank


20


is tested in the same manner as act A


5


. If a leak is found, corrective repair work may be undertaken immediately and retested in act B


4




a


, as described above in act A


5




a


. Upon completion of the repair and verification of the repair work, apparatus


80


should be disconnected in act B


5


in the same manner as set forth above in act A


6


above.




While the detailed description relates to a locomotive fuel tank repair work, the present invention is relevant to all fuel tank repair work. While the invention has been described by way of an example embodiment, it is understood that the words that have been used herein are words of description, rather than words of limitation. Changes may be made, within the purview of the appended claims, without departing from the scope and spirit of the invention in its broader aspects. Although the invention has been described herein with reference to particular structures, materials, and embodiments, it is understood that the invention is not limited to the particulars disclosed. The invention extends to all equivalent structures, mechanisms, acts and uses, as are within the scope of the appended claims.



Claims
  • 1. A method for preparing a fuel tank for repairs and verifying the repair work using an apparatus, said apparatus comprising a supply system, a relief system, and plurality of connectors, wherein each of said supply system and relief system is coupled to said fuel tank, said method comprising:connecting the apparatus to the fuel tank, wherein the supply system is connected to a first portion of the tank, and the relief system is connected to a second portion of the tank; purging the fuel tank of oxygen to a certain level using a certain gas by providing the certain gas through the supply system and releasing the oxygen through the relief system until a level of the oxygen in the fuel tank reaches the certain level; closing, to an environment of the fuel tank, openings on the fuel tank; repairing the fuel tank while maintaining the certain level of oxygen in the fuel tank, the repairing being associated with a repaired area of the fuel tank; providing the certain gas through the supply system to the fuel tank to pressurize the fuel tank with the certain gas to a certain pressure level; maintaining the certain pressure level for a specified period of time; and performing an inspection of the repaired area of the fuel tank.
  • 2. The method according to claim 1 further comprisesrepairing any remaining repairs found following the inspection of a repaired area; re-pressurizing the fuel tank by supplying the certain gas through the supply system to the fuel tank; re-testing the repaired area; and repeating the repairing of any of the remaining repairs, re-pressurizing the fuel tank, and retesting the repaired area until the retesting indicates that the remaining repairs are complete.
  • 3. The method according to claim 2, wherein said certain level of oxygen is below about 6 percent.
  • 4. The method according to claim 2 wherein said certain level of oxygen is measured by at least one gas inspector.
  • 5. The method according to claim 2, wherein said certain pressure level is between 1.8 and 2.0 psi.
  • 6. The method according to claim 2, wherein said specified period of time is at least 10 minutes.
  • 7. The method according to claim 2, wherein said inspection includes at least one of an audible inspection or visual inspection of the repair work.
  • 8. The method according to claim 2, wherein said certain level of oxygen is below about 6 percent, said certain level of oxygen is measured by at least one gas inspector, said certain pressure level is between 1.8 and 2.0 psi, said specified period of time is at least 10 minutes, and said inspection includes at least one of an audible inspection and a visual inspection of the repair work.
  • 9. The method according to claim 1, wherein said certain level of oxygen is below about 6 percent.
  • 10. The method according to claim 1 wherein said certain level of oxygen is measured by at least one gas inspector.
  • 11. The method according to claim 1, wherein said certain pressure level is between 1.8 and 2.0 psi.
  • 12. The method according to claim 1, wherein said specified period of time is at least 10 minutes.
  • 13. The method according to claim 1, wherein said inspection includes at least one of an audible inspection and a visual inspection of the repair work.
  • 14. The method according to claim 1, wherein said certain level of oxygen is below about 6 percent, said certain level of oxygen is measured by at least one gas inspector, said certain pressure level is between 1.8 and 2.0 psi, said specified period of time is at least 10 minutes, and said inspection includes at least one of an audible inspection and a visual inspection of the repair work.
Parent Case Info

This application claims the benefit of priority from provisional U.S. patent application Ser. No. 60/161,372, filed in the. U.S. Patent and Trademark Office on Oct. 26, 1999, herein incorporated by reference in its entirety.

US Referenced Citations (2)
Number Name Date Kind
5295391 Mastandrea et al. Mar 1994 A
5668308 Denby Sep 1997 A
Foreign Referenced Citations (1)
Number Date Country
9809702 Apr 1999 ZA
Non-Patent Literature Citations (2)
Entry
Database WPI, Week 199931, Derwent Publications Ltd., London, GB; AN 1999-37521, XP002164177.
International Search Report PCT/US 00/41175 mailed Apr. 9, 2001.
Provisional Applications (1)
Number Date Country
60/161372 Oct 1999 US